Answer:
a
Step-by-step explanation:
follows geometric sequence. starting value is 1/3 and is multiplied by 1/3 every time
There are 2 roots so the only way to complete the square is,
![y=2x^2+8x-9\\y=2[(x^2+4x)]-9\\y=2[(x^2+4x+4)-4]-9\\y=2[(x+2)^2-4]-9\\y=2(x+2)^2-8-9\\y=2(x+2)^2-17](https://tex.z-dn.net/?f=y%3D2x%5E2%2B8x-9%5C%5Cy%3D2%5B%28x%5E2%2B4x%29%5D-9%5C%5Cy%3D2%5B%28x%5E2%2B4x%2B4%29-4%5D-9%5C%5Cy%3D2%5B%28x%2B2%29%5E2-4%5D-9%5C%5Cy%3D2%28x%2B2%29%5E2-8-9%5C%5Cy%3D2%28x%2B2%29%5E2-17)
Just factor 2 out of 2x^2+8x (just ignore the -9) then find the number that will make the terms be able to complete the square.
then complete the square and multiply 2 inside the brackets.
subtraction as you already get the vertex form and know how to complete the square.
Vertex Form: 
5<em>x</em>² - 7<em>x</em> + 2 = 0
5(<em>x</em>² - 7/5 <em>x</em>) + 2 = 0
5(<em>x</em>² - 7/5 <em>x</em> + 49/100 - 49/100) + 2 = 0
5(<em>x</em>² - 2 • 7/10 <em>x</em> + (7/10)²) - 49/20 + 2 = 0
5(<em>x</em> - 7/10)² - 9/20 = 0
5(<em>x</em> - 7/10)² = 9/20
(<em>x</em> - 7/10)² = 9/100
<em>x</em> - 7/10 = ± √(9/100)
<em>x</em> - 7/10 = ± 3/10
<em>x</em> = 7/10 ± 3/10
<em>x</em> = 10/10 = 1 or <em>x</em> = 4/10 = 2/5
The correct answer for this question is: The <span>period(s) of time where the average rate of changes to zero is </span>"b.The average rate of change of temperature is 0 from 2 PM to 4 PM and also from 10 AM to 8 PM; Nothing can be concluded about the actual temperature fluctuation."
